The kidney excretes waste products by producing urine and, at the same time, plays an important role in maintaining homeostasis of electrolytes and water in a body. When the kidney function is lost, since water and a variety of toxic components are accumulated, and clouding of consciousness, dyspnea due to lung edema, or hyperpotassemia results in death, it is necessary to conduct artificial dialysis. The number of patients undergoing artificial dialysis in Japan has reached about 300 thousands, and is also steadily increasing currently. The primary cause for artificial dialysis introduction is diabetes which occupies about 45% of the number of introduction patients. In addition, the kidney also plays an important role as an endocrine organ, regulates blood pressure by producing renin, and is involved in bone metabolism and maintenance of erythrocytes by activation of vitamin D and production of erythropoietin. For this reason, in renal failure, abnormality of blood pressure and a bone, and severe anemia are seen. For anemia associated with renal failure, treatment by administering erythropoietin a few times per week is performed currently, but administration throughout the life is necessary, and this causes an increase in medical expenses.
When patients have fallen into end-stage renal failure due to a kidney disease such as diabetic nephropathy, chronic glomerular nephritis, renal sclerosis etc., two therapeutic methods: kidney transplantation from corpses and living bodies and artificial dialysis through blood or peritoneum are conducted. Kidney transplantation is fundamental treatment which can completely compensate for the damaged renal function, but it could not have become a general therapeutic method due to chronic deficiency of donors. On the other hand, artificial dialysis imposes severe dietary restriction or periodic hospital visit on patients, while since it is mere compensation for the filtration function of the kidney, it causes long term complication. As the new treatment to replace them, regenerative medicine is paid attention.
Although in vitro construction of a variety of types of tissues from pluripotent stem cells has been successful, there has still been no successful case of in vitro nephrogenesis, and establishment of methodology thereof has been waited. This is mainly due to that details of the mechanism thereof have not been clarified due to the embryological complexity of an in vivo renal differentiation process. That is, unlike other main organs, the kidney is formed via a complicated process associated with formation of three primordia: two temporary primordia (pronephros, mesonephros) located anteriorly, and further, metanephros located posteriorly and differentiating into the adult kidney, in its developmental process. Furthermore, in order that the artificially reconstructed kidney functions, essential construction of a three-dimensional structure including both the “glomerulus” and the “renal tubule”, constituting a “nephron” which is its functional unit further enhances its technical difficulty.
The kidney is developed from the metanephros which develops at the most posterior part of the fetal body trunk. The metanephros is formed by interaction between two precursor tissues, that is, the metanephric mesenchyme and the ureteric bud. Previously, it has been shown by cell lineage analysis that both of the metanephric mesenchyme and the ureteric bud are developed from the intermediate mesoderm expressing a transcription factor, Osrl, which appears at day 8.5 of the viviparity (E) (Non-Patent Literature 1: Mugford et al., Dev Biol 324, 88-98, 2008). However, the mechanism which is a basis of by what growth factor signal the initial stage mesoderm is differentiated into the intermediate mesoderm has not been revealed. In addition, in a process in which the intermediate mesoderm is developed into the metanephros, the importance of a posterior Hox gene group posterior to the intermediate mesoderm has been reported (Non-Patent Literature 2: Mugford et al., Dev Biol 319, 396-405, 2008; Non-Patent Literature 3: Wellik et al., Genes Dev 16, 1423-1432, 2002). However, how the anterior-posterior axis is formed in the intermediate mesoderm, a posterior Hox gene is developed, and the metanephric mesenchyme is formed (posteriorization) has not been clarified yet.
The kidney is formed by interaction of two tissues of the metanephric mesenchyme and the ureteric bud derived from the mesoderm, and a main structure such as the “glomerulus” and the “renal tubule” contained in the nephron which is its functional unit is derived from the former (metanephric mesenchyme). The inventors have previously reported that a progenitor cell (metanephric nephron progenitor cell) which is the source of the nephron exists in the metanephric mesenchyme at a mouse fetal stage, and also developed a method of detecting it (Non-Patent Literature 4: Osafune, Nishinakamura et al., Development 133, 151-161, 2006). In addition, a method of inducing the intermediate mesoderm from an iPS cell, by culturing the iPS cell in the presence of activin A and Wnt, then, culturing the cell in the presence of BMP and Wnt has been reported (Patent Literature 1: international publication: WO2012/011610). However, there is no report that the induction of the “metanephric nephron progenitor cell” which can reconstruct both of the glomerulus and the renal tubule from pluripotent stem cells has been succeeded.